1. Field of the Invention
The present invention relates to a system for correcting the output of a tank internal-pressure sensor in an evaporative fuel processing device comprising a fuel tank, a canister filled with an adsorbent for adsorbing the evaporative fuel generated in the fuel tank, and a pressure regulating valve provided in an intermediate portion of an evaporative fuel passage connecting the fuel tank and the canister. The pressure regulating valve is opened in response to the pressure in the fuel tank reaching a predetermined pressure. The system also includes a tank internal-pressure sensor provided in the fuel tank or in the evaporative fuel passage between the fuel tank and the pressure regulating valve and means for correcting the output of the sensor.
2. Description of the Prior Art
Systems for correcting the output of a tank internal-pressure sensor are conventionally known, for example, from Japanese Patent Application Laid-Open No. 195896/93. In this known system, the inside of the fuel tank is opened to the atmosphere at a cold start of the engine in which it is difficult to generate an evaporative fuel within the fuel tank, and the output delivered at that time from the tank internal-pressure sensor is set as a reference value.
In this known system, however, the inside of the fuel tank is opened to the atmosphere through the canister at the cold start of the engine and hence, internal pressure in the fuel tank does not completely reach the atmospheric pressure. In the case where the internal pressure in the fuel tank does not completely reach atmospheric pressure, there is a possibility that an error in detection by the tank internal-pressure sensor is increased by using the output from the tank internal-pressure sensor as a reference value.